Monolith catalyst test system and method for its use

ABSTRACT

A system and method for non-destructive testing of a monolith catalyst element includes a flat surface on which a monolith catalyst can be placed and a portion of the catalyst sealed against a piping arrangement located above and below the flat surface. A test fluid passes between the piping and therefore through the portion of the sealed catalyst section. Ports located in the piping allow for sampling of the fluid before and after the catalyst section. The catalyst element may then be repositioned on the flat surface for testing of a second portion of the element.

BACKGROUND OF THE INVENTION

This invention relates generally to systems, apparatuses, and methodsuseful in testing the performance of a monolith catalyst. Morespecifically, this invention relates to systems, apparatuses, andmethods for non-destructive testing of a monolith catalyst like thoseused in industrial engine emission control. Notwithstanding the above,the underlying principles could be used for testing any large monolithcatalyst element.

There are two methods for testing the activity of a monolith catalyst.The first method removes a small portion of the catalyst element, placesthat portion or sample core into a small test system, and uses syntheticgas mixtures to test the core and determine the overall activity of thecatalyst. For example, catalysts used in industrial engines have outsidedimensions from about 6 to 40 inches across and the removed core can beabout 1 inch diameter. The second method tests the entire catalystelement by installing the element into a system that passes eitherengine exhaust or a synthetic gas mixture over the element.

The first method, sampling, has two major disadvantages: sampling errorand catalyst damage or failure. Sampling error comes about because theactivity of the catalyst element can vary across its face. Therefore,the sample core may test at higher or lower activity than the element asa whole and introduce significant sampling error into the test results.Catalyst failure comes about in a couple of ways. First, becausereinstalling the core into the element is challenging, the hole createdby the removed sample core is often plugged to prevent flow passingthrough it. This reduces the available catalyst volume and detrimentsthe performance of the catalyst element as a whole. Additionally, anyleakage around the plug or reinstalled core impairs performance. Fear ofdamaging the element leads people to test a limited amount of it—andthereby increase sampling error—because every core removed presentsanother opportunity to damage the overall element. Second, the processof removing the core can cause loss of coating material in the coreitself. This not only detriments the analysis but because some catalystelements have layers of metal foil that are not bound together, theelement can either fall apart or destroy its cellular structure. Roughlyhalf of all industrial engine monolith catalyst manufacturers do notaffix layers and cutting operations can shake off about half of thecoating.

The second method, whole element testing, eliminates sampling error andcatalyst failure, but it too has a couple of problems. First, the methodis resource and cost intensive because an engine has to be used togenerate the test gas or a synthetic gas mixture must be used. If asynthetic gas mixture is used, tanks must be purchased to supply the gasand the entire gas stream must be heated above 700° F. If an engine isused, it must be fueled and maintained. And the engine also introduceserror to the testing because a wide range of factors affect engineexhaust, factors such as engine wear, ambient conditions, fuel quality,and oil quality. Second, the quality of data obtained from the testdepends upon having the correct “space velocity,” that is, the correctratio between the flow rate of gas through the catalyst and the volumeof catalyst material. Because of the wide range of catalyst sizes andshapes employed by the various catalyst suppliers, the tester must haveright equipment, jigs and fixtures to hold each size and shape in thegas flow. This leads to having a lot of equipment on-hand and the timeconsuming changeover that results. Additionally, the tester must producesufficient gas flow for the specific catalyst either by using a seriesof engines or supplying a large amount of synthetic gas.

In summary, the first method, sampling, introduces significant samplingerror and destroys a portion of the catalyst element. The second method,whole element testing, is very inefficient and difficult to set up giventhe wide range of sizes and shapes of catalyst elements employed by theindustry.

SUMMARY OF THE INVENTION

A monolith test system made according to this invention allowsefficient, non-destructive activity testing of monolithic catalystelements. The system allows the activity of a small section of theoverall catalyst element to be tested without removing it from theelement. This is accomplished by directing a gas through pipes havingmeans of sealing them against the surface of the catalyst being tested.In principle, any temperature, gas flow rate, and pipe diameter can beused. Multiple runs are conducted at different regions of the element'sface in order to assess the activity level of the whole. The gascomposition could also be varied to allow testing of any catalystsystem.

Objects of this invention include providing an activity test system formonolithic catalysts that does not damage the catalyst, allows adequatesamples to be tested in an efficient manner, and does not requiredifferent jigs and fixtures to accommodate different sized and shapedcatalysts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a preferred embodiment of a test standwhich practices the system and method of this invention. Various panelshave been removed from the stand in order to present the stand'scontents. A catalyst element to be tested is placed on the stand's tabletop and a section of the element is sealed between a catalyst inlet pipewhich delivers a test fluid and a catalyst outlet pipe which receivesthe test fluid after it has passed through the section. The stand allowsvarious sections of the catalyst to be tested.

FIG. 2 is an front elevation view of the test stand of a FIG. 1. Ablower supplies a main fluid stream which is passed through a heater toheat it to the desired temperature. A propane cylinder supplies a testfluid which bypasses the heater and mixes with the heated main fluidstream. The catalyst outlet pipe is vertically displaceable relative tothe table top.

FIG. 3 is a left side elevation view of the test stand of FIG. 1. A portlocated on the catalyst outlet pipe allows for sampling of the fluidstream after it has passed through the section being tested. A similarport is located on the catalyst inlet pipe.

FIG. 4 is a right side elevation view of the test stand of FIG. 1.

FIG. 5 is an enlarged view of a section of the system of FIG. 1surrounding the catalyst inlet pipe and the catalyst outlet pipearranged to test catalyst elements in a vertical orientation.

FIG. 6 is a view of another preferred embodiment of the test standarranged in a vertical orientation.

ELEMENTS AND NUMBERINGS USED IN THE DRAWINGS AND DETAILED DESCRIPTION

-   10 Test system-   20 Test stand-   21 Table-top, flat surface-   31 Blower (source of main fluid)-   33 Blower outlet piping-   35 Heater-   37 Heater outlet piping-   41 Propane cylinder (source of test fluid)-   43 Propane piping-   50 Catalyst inlet pipe-   51 Opening-   52 Flange-   53 Gasket (sealing means)-   54 Table-top surface opening-   55 Upper end-   59 Port-   60 Catalyst outlet pipe-   61 Flange-   63 Gasket (sealing means)-   65 Lower end-   67 Screw jack (raising and lowering means)-   69 Port

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A test system 10 made according to this invention allows a section of amonolithic catalyst element to be tested without requiring a piece ofthe catalyst to be removed from the element. Although the system 10described herein is intended for use catalyst elements typically foundin industrial engines, the system 10 could be used to test anymonolithic catalyst element for any industry. These elements areespecially common in a range of environmental compliance process units.

Testing is accomplished by providing a means of conveying fluid throughthe catalyst element and allowing those means to test different areas orsections of the element. A preferred embodiment uses a test stand 20which includes piping above and below the catalyst as the conveyingmeans, air as the main fluid and propane as the test fluid, that is, theconstituent fluid acted upon by the catalyst element. A blower 31creates the air stream and passes it into a blower outlet piping 33which is connected to a heater 35. The heater 35 heats the blown airstream to a desired test temperature. The heated air stream then passesinto a heater outlet piping 37. A propane cylinder 41 introduces apropane stream into a propane piping 43 which bypasses heater 35.Downstream of the heater 35, the heated air stream and the propanestream meet and pass through a static mixer (not shown) located in acatalyst inlet pipe 50 and become thoroughly mixed together (“the mixedstream”).

Note that compounds other than propane may be used as the test fluid.Propane was selected as the test fluid here because of its standardcommercial composition across the country, local availability, generalfamiliarity with its storage and use due to its widespread use as acooking fuel for barbeque grills, the odorant that is incorporated in itas an indicator of leakage, its low cost compared to other potentialtest compounds and the fact that it is often found in the normalconstituents of the exhaust from industrial engines. However, anycompound that is gaseous at the desired test temperature and capable ofbeing acted upon by the catalyst element can be used as the test fluid.

The mixed stream of propane and heated air then proceeds to an opening51 at the upper end of catalyst inlet pipe 50. The opening 51 issurrounded by a flange 52 that is flush with a large, table-top, flatsurface 21 of the test stand 20 which supports the catalyst element.There is an opening 54 in the table-top surface surrounding the upperend of the catalyst inlet pipe. A gasket 53 located at the upper end 55of the catalyst inlet pipe 50 provides sealing means against the loweror inlet face of the catalyst section being tested. The test stand 20may be provided with means to adjust the height of the opening 51relative to the flat surface 21 to ease the movement of the catalystelement across the flat surface 21 without damaging the gasket 53. Athermocouple (not shown) placed at the inlet face of the catalystsection controls the temperature of the mixed stream. Preferably, thethermocouple is installed with its tip flush with the upper end 55 ofthe catalyst inlet pipe 50 to control the temperature of the mixedstream.

The mixed stream exits opening 51, and flows into and through thecatalyst section. A flow meter (not shown) allows measurement andcontrol of the mixed stream flow through the catalyst section. Due tothe structured nature of monolithic catalysts, the mixed stream flow isrestricted radially to the diameter of the opening 51. A catalyst outletpipe 60 is provided on the upper or outlet face of the catalyst element.The outlet pipe 60 is essentially identical to the catalyst inlet pipe50, has the same diameter opening as that of opening 51, and is alignedconcentrically relative to the inlet pipe 50. A gasket 63 located in aflange 61 surrounding the opening provides sealing means against theoutlet face of the catalyst section being tested. A thermocouple (notshown) is installed with the tip flush with the opening of the outletpipe to allow measurement of the mixed stream at the outlet side of thecatalyst section. The mixed stream then passes through the outlet pipe60 and is exhausted.

Either the flat surface 21 or the catalyst outlet pipe 60 must beprovided with means to raise or lower it and allow the catalyst elementto be installed and removed from the test stand 20. In a preferredembodiment, the catalyst outlet pipe 60 is raised and lowered. Theraising and lowering means is a pipe expansion joint 65 installed in thelength of the outlet pipe 60 and a screw jack 67 is used to raise andlower the outlet pipe. Other raising and lowering means could be used.

This system provides a method for sealing a pipe or tube to the inletand outlet faces of the catalyst. This allows different sections of thecatalyst to be tested without removing a piece of the catalyst. Forexample, on a 32-inch diameter catalyst element, 6 to 8, 2-inch sectionscan be tested. On a 12-inch diameter catalyst element, 3 2-inch sectionscan be tested. The minimum, maximum and average performance can then becalculated. The invention also allows one or both sealing surfaces to bemoved in a vertical direction to allow testing of a range of catalystthicknesses. Although the example illustrated in FIGS. 1-4 shows thecatalyst element in a horizontal orientation with the catalyst inlet andoutlet pipes 50, 60 arranged vertically in relation to the catalyst,test stand 20 could be configured with the catalyst inlet and outletpipes 50, 60 arranged to test catalyst elements in a verticalorientation as shown in FIG. 5 (or some other angular orientation). Anessential feature of the invention is aligning the catalyst inlet andoutlet pipes 50, 60 with each other and placing the pipes 50, 60 insealing relationship to the catalyst element in order to test anysection of that element without having to remove a portion of it orinstall a separate reactor.

Regardless of the orientation of the catalyst element, ensuring goodsealing is key to getting consistent results when performing catalysttests. The traditional way of accomplishing good sealing, and the wayused in the test methods discussed in the Background section, is toinstall the catalyst into a piping system sealed with typical pipingmethods. Test system 10 employs a different approach, namely, clamping asection the catalyst element between two flexible piping structures 50,60 having appropriate sealing means 53, 63. This different approachallows the purposes of this invention to be accomplished.

To determine the activity of the catalyst at the section of the elementtested, one or more compounds or species of the mixed stream must beexpected to be affected by the catalyst at the test temperature. Themixed stream is sampled with the use of two ports 59, 69 in the inletpipe 50 upstream of the catalyst and the outlet pipe 60 downstream ofthe catalyst, respectively. This allows the concentration of the speciesof interest to be determined before and after the catalyst. Theconcentrations can then be used to determine a conversion across thecatalyst.

The concentrations can be measured through the use of an analyticalinstrument that is capable of detecting the compound(s) being introducedto the catalyst. A listing of such instruments includes but is notlimited to portable gas measuring equipment for monitoring engineexhaust, flame ionization detector, and gas chromatograph. The type ofanalytical instrument used is not critical to the operation of the testsystem 10 as any of these instruments can provide the information neededto assess the performance of the catalyst being evaluated. The operatormakes the choice of instrumentation based on the cost to purchase andthe complexity of operation for the instrument against the degree ofsensitivity and resolution they desire in the data obtained.

The preferred embodiments disclosed herein are the result of a number ofdesign iterations. The original test system was built with a smallerprimary heater and included a heat exchanger. The gas flowed through theheat exchanger, through the heater, through the catalyst, and thenthrough the heat exchanger again. The purpose of the heat exchanger wasto recover heat from the outlet gas stream and use it to preheat theinlet gas in order to reduce energy demands. This design took up morespace and did not reliably achieve the desired reaction temperature atthe desired flow rate.

A second iteration involved removing the heat exchanger and adding asecond heater in series with the first heater (i.e., the gas flowed overone heater and then over the second). This configuration allowed thedesired temperature to be achieved at the desired flow rate, but theheaters failed after an unacceptably short period of operation.

A third iteration placed the two heaters in parallel (i.e., the gas flowwas distributed over both heaters simultaneously). This configurationdid not allow the desired temperature to be achieved, so a third heaterwas placed upstream of the other two. The gas flowed over the singleheater and then was distributed over the other two heaters. Thisthree-heater layout allowed the reaction temperature to be achieved atthe desired flow rate with a reasonable heater life.

After appropriate flow rates and temperatures were achieved, the testgas injection system was tested. Initially, it appeared the injectionsystem was working as expected, but then inconsistencies began to appearas the testing progressed because the test gas was not fully mixed inthe bulk gas stream. The uneven distribution of gas led to a radialconcentration gradient in the pipes and across the catalyst and causedinconsistent results. At the time, the test gas was conveyed through a¼-inch tube which was connected to the wall of the test stand pipe. Thegas appeared to be staying against the pipe wall instead of dispersinginto the entire stream.

To correct the uneven distribution of test gas, a series of nozzles thatdirected the test gas flow into the center of the pipe were prepared andtested. The nozzles failed to correct the distribution problem on theirown. A nozzle was left on the test gas system, and a static mixingdevice was added downstream from the test gas injection point. Thisfinally led to good mixing of the test gas into the bulk stream.

As testing continued, the flat surface or table top that the catalyst isplaced on for the tests warped and prevented proper sealing of theflanges at the catalyst face. To correct this, a new table top wasdesigned. The new table top used a different grade of stainless steel(preferably, for example, AISI type 304 or 409) having a smallercoefficient of thermal expansion. Thicker steel was used to help controlthe warping. A larger circle was also cut around the heated pipe. Thelarger opening lowered the temperature gradient to which the steel wasexposed. These three changes led to a significant reduction in thewarping that was taking place and allowed the flanges to consistentlyseal against the face of the catalyst section being tested.

The final phase of testing involved establishing appropriate testconditions. The goal of this testing was to determine the change inactivity of a catalyst after a catalyst cleaning procedure. Testconditions (specifically, flow rate and temperature) needed to beselected to allow changes in catalyst performance to be detected. If thetemperature was too high or the flow rate too low, most catalysts wouldachieve complete or nearly complete conversion of the test gas, and itwould not be possible to distinguish active and inactive catalysts. Ifthe test temperature was too low or the flow rate was too high, evenactive catalyst would not perform well and all the catalysts wouldcluster tightly near zero conversion. Routine experimentation of thekind typically done in the art led to a range of temperatures and flowrates that allowed the activity before and after the cleaning process tobe differentiated.

A test system 10 made according to this invention has immediatepracticality in the area of industrial engine exhaust emissions. Thesystem 10 allows an engine catalyst to be tested in order to determinethe extent of deactivation the catalyst has undergone during use. Thecatalyst can be cleaned and retested to determine if it still has usefullife remaining or if it has been deactivated beyond recovery. Becausethe cleaning process is significantly more cost effective thanpurchasing a new catalyst, engine operators have been willing to have itdone when using the prior art test methods but risk extended downtime byreinstalling a cleaned but deactivated catalyst. The cleaned,deactivated catalyst would fail emissions testing and the operator wouldhave to uninstall and replace the catalyst. Additionally, beyond thelabor costs incurred by reinstalling a deactivated catalyst, theoperator risks exposure to fines and penalties from EPA and respectivestate agencies because the engine's emissions are no longer incompliance with operating permits. Having an efficient testing procedurelike that provided by system 10 allows the catalyst to be cleaned andtested for less than the cost of a new catalyst element while providingoperators a method of determining the activity of the catalyst prior toits reinstallation.

The test system 10 also provides a non-destructive method of efficientlytesting monolithic catalyst elements. As discussed in the Backgroundsection, existing methods require removing part of the element fortesting or installing the entire element into a test system. This risksleakage or catalyst failure in the first case or, in the second case, istoo expensive to be used.

Although preferred embodiments of a test system and method have beendisclosed, changes can be made in its construction or arrangement ofparts and steps. Therefore, the scope of the invention is limited onlyby the following claims and equivalent elements thereof.

What is claimed:
 1. A non-destructive testing system comprising: asurface a catalyst inlet piping a catalyst outlet piping each arrangedon opposing sides of the surface, the catalyst inlet and outlet pipinghaving a same diameter opening and aligned concentrically to oneanother; sealing means located at an opposing facing end of the catalystinlet and outlet piping same diameter openings, respectively, forsealing the same diameter openings against an inlet face and an outletface of a portion of a monolith catalyst element when a monolithcatalyst element is resting on the surface; and means to change therelative longitudinal distance between at least one of the inlet andoutlet ends and the surface; the surface having an opening arrangedconcentric to the catalyst inlet and outlet piping and being larger indiameter than the catalyst inlet piping and creating a circumferentialgap between the surface and the catalyst inlet piping.
 2. A systemaccording to claim 1 further comprising a source of a main fluid streamand a source of a test fluid stream, the catalyst inlet piping being incommunication with the main fluid and test fluid sources.
 3. A systemaccording to claim 2 further comprising a heater located between thesource of the main fluid stream and the catalyst inlet piping.
 4. Asystem according to claim 3 further comprising means for the test fluidstream to bypass the heater.
 5. A system according to claim 1 furthercomprising a mixer for mixing a main fluid stream and a test fluidstream with one another.
 6. A system according to claim 1 furthercomprising each of the catalyst inlet and outlet pipes having a portthrough which a fluid passing through the pipe may be sampled.
 7. Asystem according to claim 1 wherein the surface is a flat surface.
 8. Asystem according to claim 1 wherein the surface is arranged in ahorizontal plane.
 9. A system according to claim 1 wherein the surfaceis arranged in a vertical plane.
 10. A method for non-destructivetesting, the method comprising the steps of (i) placing the monolithcatalyst element on a surface having a catalyst inlet pipe located belowthe surface and a catalyst outlet pipe located above the surface, thecatalyst inlet and outlet pipes having a same diameter opening andaligned concentrically to one another, the surface having a largerdiameter opening than the catalyst inlet pipe and being arrangedconcentric to the catalyst inlet and outlet pipes; (ii) sealing the samediameter openings of the catalyst inlet and outlet pipes against aninlet face and an outlet face, respectively, of a portion of the placedmonolith catalyst element; and (iii) passing a test fluid stream betweenthe catalyst inlet and outlet pipes and through the sealed portion ofthe placed monolith catalyst element; wherein the passing step systemallows activity of the sealed portion of the placed monolith catalystelement to be tested without removing it from the monolith catalystelement.
 11. A method according to claim 10 further comprising the stepsof: mixing a main fluid stream with the test fluid stream, the mixingstep occurring before the passing step.
 12. A method according to claim11 further comprising the step of heating the main fluid stream, theheating step occurring before the mixing step.